1. Field of the Invention
The present invention relates generally to a wireless power transmission system, and more particularly to, a method of controlling power in a power transmission transmitter.
2. Description of the Related Art
Wireless charging or contactless charging technologies have recently been developed and applied to many different electronic devices. The wireless charging technology using wireless power transmission and reception enables, for example, a battery of a cell phone to be automatically charged just by placing the cell phone on a charging pad without a need of a separate charging connector. The wireless charging technology wirelessly charges electronic products and eliminates the need for a wired charger, thus contributing to waterproof ability and portability of the electronic products.
Among the wireless charging technologies, a resonance based charging method is done as follows. When a power receiver that needs to be charged is located in an area of a power transmitter for transmitting wireless power, the power transmitter may charge the power receiver. If a plurality of power receivers are placed in a charging area of a single power transmitter, the power demanded at each power receiver may be different from transmission power. Thus, charging for each power receiver needs to be efficiently conducted.
In this regard, the conventional power transmitter sets up a voltage reference for power control to efficiently supply the power to the power receiver. However, charging efficiency may vary depending on various charging conditions, such as the power receiver's characteristics, hardware design, a distance between the power receiver and the power transmitter, a charging position, etc. If the power transmitter can transmit power that enables the power receiver to achieve its highest power reception rate, it can lead to more efficient charging.